The present invention relates to fluorine-doped diamond-like coatings on substrates and, more particularly, to such coatings on flexible substrates, precision-edged substrates, and electrosurgical instruments.
The preservation of sharp edges is important for many products and industries. Many industrial blades and medical tools are only useful if their sharp edges can be maintained for reasonably long periods of time. The sharpness is the result of the precision of the edge formed by the substrate and any coatings thereon. Razor blades, for example, have an edge formed by producing a radius of curvature at the blade""s extreme tip from about 75 to about 1000 angstroms. For comparison, a human hair has a width of about 100 micrometers. Such precise substrate edges are often coated to preserve the precision of the edge by attempting to inhibit its degradation.
Precision edge degradation can be caused by corrosive and/or erosive forces. Razor blades, for example, dull quite easily; to an extent, immediately upon first use. Steel used for razor blades is therefore often coated first with a sputtered metal coating, followed by a coating of polytetrafluoroethylene (PTFE). While the PTFE coating is usually tens to thousands of angstroms thick, it is substantially removed from the blade upon first use. Enough PTFE survives to provide a measure of continued lubrication. However, the PTFE coatings do not prevent the degradation of the precision edge.
Dulling of precision edges may be due to an increase in the radius of curvature at the blade""s extreme tip, cracks, chips or breaks at the edge causing a jagged edge, erosion of edge material, or a combination of these factors. For razor blades, the degradation of the precision edge causes increased friction and user discomfort. The blade is then replaced, or if a part of a disposable implement, the entire razor is discarded. For more expensive cutting implements in industrial or medical fields, etc., the dulling of precision-edged tools results in the need for sharpening or re-edging, which increases costs.
The depositing of harder material coatings has been tried in an attempt to preserve edge integrity. For many applications, the coating should also have excellent thermal stability; i.e., be able to withstand extreme heat, as from use itself (saw blade) or from sterilization procedures (autoclaving surgical tools).
Metal-based coatings such as steel, zinc, aluminum, chromium, nickel, cadmium, tantalum, palladium, boron, silicon, copper, gallium, rhenium, and alloys thereof, have demonstrated precision edge preservation and are used in many industries to provide protective coatings for sharp edges. However, coatings made from these materials are generally suitable only for metallic substrates.
Silicate based coatings are known to be resistant to air, acid, alkali, and gases at elevated temperatures. However, coatings made from silicates are not particularly strong materials and would not provide appropriate protection for precision edges.
Certain ceramic materials have good corrosion resistance and could conceivably be used as edge-preserving coatings. However, ceramics are brittle and subject to thermal shock failure. They are typically rough and porous and would not provide the desired low friction.
Certain hard diamond-like coatings (DLCs), have been tried. However, a coating must not only be hard, it must have excellent adherence to the substrate. Known DLCs often require an interlayer to adhere them to a substrate. For some articles, such an interlayer may not pose a problem. However, to preserve a precision edge, the total thickness of all coatings must not appreciably increase the radius of curvature at the extreme tip of the edge, which is very small. Further, the additional process of depositing interlayers between the DLC and the substrate increases the production cost. This can be significant, and even economically unsound for low cost items, such as disposable razors and razor blades.
Therefore, a strong, hard, highly adherent, temperature, pH and chemical insensitive coating that can be applied to both metal and non-metal surfaces to preserve precision edges without applying interlayers, would be highly desirable.
It is also desirable to provide many types of articles, such as cookware, industrial tools, or medical tools, with a release or non-stick coating so that sticky residues can be removed easily as the article is cleaned. Non-stick coatings include, for examples, fluorocarbon resins such as polytetrafluoroethylene or silicon resins.
Articles typically having a non-stick coating include electrosurgical blades. In electrosurgical procedures, an electrosurgical instrument is energized by a radio frequency voltage for cutting tissue and/or coagulating blood through cauterization. Such instruments commonly incorporate a conductive blade in either a monopolar or bipolar system. Although the electrosurgical instruments have proved effective for controlling bleeding during surgery, a common problem with the instruments is tissue sticking to the cutting surface and, consequently, a reduction in cutting efficiency that requires early replacement of the cutting element. One approach to this problem has been to coat the cutting element with a non-stick material to which cauterized tissue is less likely to adhere. Of course, such coating material must be suitable for passing electrosurgical current or at least the coating must be arranged to allow passage of current from the cutting surface to the tissue.
Although the coating of electrosurgical instruments with non-stick materials has improved the efficiency of surgical procedures, the known coating materials have numerous deficiencies. For instance, the coatings have unsatisfactory electrical conductivity, adhere poorly to the substrate, tend to degrade under the conditions used during surgery, and undergo surface corrosion and pitting as a result of repeated sterilization cycles.
Also, there is an increasing need for integrating passive and active devices such as resistors or capacitors on flexible substrates. The use of interconnect technology with discrete components is not amenable for multilayering, high cost assembly, unfavorable size to weight ratio, large equipment cost and multiple processing steps. Use of thin film passives resistors and capacitors excludes the requirement for solder interconnects, facilitates integration with multilayering capability and excellent size to weight ratio. Thus, use of thin dielectric coatings on flexible substrates like polyimides or high temperature polymers is becoming important. The use of integrated resistors and capacitors in Multi-layer Chip Module (MCM) and FLEX circuitry is one area for use of coatings on flexible substrates. A coating that can be used with any MCM technology including flip chip, surface mount or direct chip attach is desirable.
Presently, resistors and capacitors are made as discrete components and mounted by solder and wire bonding. This involves high cost assembly, costly equipment for bonding an soldering, unfavorable size to weight ratio and incompatibility to building multi-layered circuitry. The present invention is directed to overcoming these deficiencies.
The present invention is directed to an article including a substrate coated with a fluorine-doped diamond-like coating, wherein the coating includes a diamond-like composition containing carbon, silicon, oxygen, hydrogen, and fluorine In one embodiment, the invention relates to a flexible substrate coated with a fluorine-doped diamond-like coating. The coating contains carbon, silicon, oxygen, hydrogen, and fluorine, and is preferably coated to a thickness of about 0.05 micron to about 10 microns.
In another embodiment, the invention relates to a precision-edged substrate coated with a fluorine-doped diamond-like coating containing carbon, silicon, oxygen, hydrogen, and fluorine.
In yet another embodiment, the invention relates to an electrosurgical instrument coated with a fluorine-doped diamond-like coating. The coating contains carbon, silicon, oxygen, hydrogen, and fluorine.
In a further embodiment, the invention relates to a substrate coated with a fluorine-doped diamond-like coating which contains carbon, silicon, oxygen, hydrogen, fluorine, and an additional dopant.
The present invention further relates to a method of making an article comprising a substrate coated with a fluorine-doped diamond-like coating which includes positioning the substrate in a vacuum deposition chamber and depositing a diamond-like composition containing carbon, silicon, oxygen, hydrogen, and fluorine onto the substrate by co-deposition of clusterless particle beams comprised of ions, atoms, or radicals of the carbon, silicon, oxygen, hydrogen, and fluorine. The mean free path of each particle species is in excess of the distance between its source and the growing particle coating surface of the substrate.